The present invention relates to a setting member for controlling the quantitative flow of a fluid, in particular for regulating the idling speed of an internal combustion engine, having an electromagnet and an armature which is movable by the electromagnet against the force of a spring.
With the electronic control of the idling speed of rotation of internal combustion engines, the engine speed of rotation upon idling is maintained constant even under the influence of changes in load. The electronic controller determines the instantaneous speed of rotation of the engine for instance from the ignition pulses, compares it in the idling range with the predetermined desired speed of rotation and supplies a pulse width-modulated signal to the setting member. This setting member controls the quantitative flow in a bypass which lies in parallel to the throttle valve. The setting member changes its effective cross section of opening in accordance with the current given off by the controller (average value) and doses the quantity of air so as to maintain a constant idling speed of rotation of the engine.
In one known setting member for the regulation of idling a piston is so displaced by means of an electromagnet the force of a spring that it increasingly releases flow openings with increasing deflection. If however, no current is fed to the electromagnet during operation in idling, as can take place by a defect in the electronic controller or in the line connections, then the setting member is brought into the closed position by the spring. Thus, the smallest possible amount of air is set, namely, merely the amount of air which is passed through the remaining gap between the closed throttle valve and the intake tube. This amount of air however is not sufficient to be able to operate the engine in idling under different operating conditions.
If, for instance, the control range of the idling control is so designed that with minimum load on the engine and therefore with optimum operating temperature and the absence of additional loads such as for instance an air conditioner or an automatic transmission, a slight idling speed of rotation is still adjusted, then, within the known setting member in the case of lower operating temperature or with gear engaged (automatic transmission), the engine would stop in the case of the failure of the electronic control.